FIX: Email threads sometimes not grouping for group SMTP (PR #13727)

This PR fixes a couple of issues related to group SMTP:

  1. When running the group SMTP job, we were exiting early if the email was for the OP because of an IMAP race condition. However this causes issues when replying as a new topic for an existing SMTP topic, as the recipient does not get the OP email which can cause threading problems.
  2. When sending emails for a new topic spun out like the issue in 1., we are not maintaining the original subject/topic title because that is based on the incoming email record, which we do not have if just creating a new topic for group SMTP. We need to create an IncomingEmail record for all new group topics with some details like the subject for cases like this.